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Old 8th Dec 2018, 6:36 pm   #1
Bazz4CQJ
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Default Please ID: 250L9634, 250L9649. Varistors?

Could anyone help me id these components which have been lurking unused in my junk box, and don't show up on Google?

They look a little bit like a large ceramic disk capacitor, about 11mm wide and ~3mm thick, but are finished off in a bright red lacquer. There's a maker's logo which is in 3 parts (looking hard through a magnifying loop);
  • within a circle, the letter S and perhaps a D
  • a middle bit which is just a graphic
  • what looks like the letters LR, but facing in reverse
I cannot recall buying them though they look fairly modern and I suspect they are some type of mains transient suppressors.

Thanks

B
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Old 9th Dec 2018, 12:45 am   #2
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Sounds very much like someone's 250L series varistor. The funny backwards LR is probably the stylized backwards UR showing it's an Underwriters Laboratory registered part.
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Old 9th Dec 2018, 3:18 am   #3
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

GE MOVs are traditionally bright red, but my V250L40 types are 21mm diameter, not 11mm.
They do not have a logo as such.
They are marked -
GE N7
V250L40

The possible "UR" implies USA manufacture.

Last edited by Radio1950; 9th Dec 2018 at 3:40 am.
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Old 9th Dec 2018, 5:19 pm   #4
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

I made a little progress; I began to recall that these could have come from Maplin about 10 years ago and sure enough they are in the Maplin cat (2009-2010) under Maplin part no.HW13P;

Transient Suppressor, 240VAC, peak current 2500A in 8uS clamping at 650VAC at 25A.

No reference to original maker and the info provided falls a long way short of a datasheet. If any one has any more info on HW13P, that would be good. I've spent ages on Google trying all kinds of tricks to find them but no success. It is, however, a example of what many of us have already learned; old catalogues can sometimes be most usefull!

B
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Old 9th Dec 2018, 9:13 pm   #5
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Hi Baz,
Have you tried a Google "image" search on that logo?
This might find the manufacturer.
Rgds
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Old 9th Dec 2018, 10:15 pm   #6
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

No, it is so small and indistinct I can barely see it through my x10 magnifier, suspect it won't photograph usefully (without a microscope). Sadly, the quality of the stuff Maplin were then selling was not great, and I don't fancy putting mains voltage on these when I can get some decent new ones for next to nothing .
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Old 10th Dec 2018, 8:44 am   #7
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Hi Baz
Because the mains here can drift up to 255V these days, I now normally use 275V MOVs.
Just in cases.
Rgds
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Old 10th Dec 2018, 2:06 pm   #8
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Yes, that sounds like sensible precaution and I see that a large proportion of the ones that some up on the auction sites are indeed 275V and from recognisable makers.

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Old 10th Dec 2018, 7:49 pm   #9
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

The SA within a circle is actually SA within a C and is a Canadian Safety Standard. The reversed RU belongs to the UL organisation which is an international safety under writer.

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Old 10th Dec 2018, 9:47 pm   #10
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Hi Baz

Christmas Music plays in background ...
" .. It's Beginning To Look A Lot Like .."

A Littlefuse MOV?
Have a very close look at the printing on this example.

The 9634 and 9649 could be date codes or option codes.
.
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Old 11th Dec 2018, 11:53 am   #11
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Beware the Ecko effect- Littelfuse is similarly tricky
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Old 11th Dec 2018, 4:01 pm   #12
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Yes, indeed, I think it is a Littlefuse MOV. I had found Littlefuse devices in my Google search but not the part number. Thank you.

Herald, could expand on the Ecko effect and the trickyness of Littlefuse?

Anyway, some 10N431K's should be here tomorrow . I'm making some improvements (hopefully) to a 30A linear psu which is showing some transients on switch on, probably related to switch bounce. It has no "soothing" components of any kind on the primary side, just a fairly cheap looking rocker switch. I thought I'd add a X2 class 0.1uF +100R resistor (new components, not Rifa!) as a snubber and and a MOV alongside that and hope that 'calm's it down. There's also a 15V Transil diode being added in to the follow-on crowbar unit.

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Old 11th Dec 2018, 5:01 pm   #13
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

The Littlefuse MOV's are listed here https://m.littelfuse.com/products/va...al-leaded.aspx. Wonderfully detailed datasheets, but it looks like they revised their numbering system and (so far) I haven't spotted 250L part numbers in there.

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Old 11th Dec 2018, 7:24 pm   #14
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Quote:
Originally Posted by Bazz4CQJ View Post

Herald, could expand on the Ecko effect and the trickyness of Littlefuse?
.

B
Yup...... Ecko should be Ekco and Littlefuse should be Littelfuse (as it is in the link).

Then we get to trickiness
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Old 11th Dec 2018, 7:27 pm   #15
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Oh yes; not sure they took any branding advice before using that name.
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Old 11th Dec 2018, 8:38 pm   #16
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Quote:
Originally Posted by Radio1950 View Post
The possible "UR" implies USA manufacture.
Strictly speaking, and also surprisingly often in practice, it implies USA sales and usage. The component can and will often be manufactured elsewhere. Not in this case, though, it seems.
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Old 11th Dec 2018, 10:20 pm   #17
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Looks like I made a littel spelling error!


I am no expert on this, and you may get a flood of advice, but ....

Consider using an NTC Inrush Current Limiter in the transformer primary.
I wouldnt bother using an MOV in the primary.

I have one of these 12V 30A linear DC PSUs.
I must check mine for spikes sometime, and see if "they" have designed it with any soft start circuit.
Mine is a generic PSU.
Do you have a circuit for yours please?

I wouldnt fret too much about a few switch-on transients in mine, and it is probably not due to switch contact bounce as such. All switches would probably show the same effects in this application.

Good luck.
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Old 11th Dec 2018, 11:40 pm   #18
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

The psu I have is a Mydel MP304 (see picture), which I think is sold in the UK by one particular ham radio dealer, but could be sold elsewhere under another name. I don't have a circuit for it, but opened it up, and as stated above, the primary side has nothing but a rocker switch alongside it.

I saw a website suggesting that the unit is a clone of a Daiwa 304 but that only uses 3 pass transistors whereas the Mydel uses 6 pass transistors, Daiwa cct attached.

Herald may advise us on transients, IIRC, he designed power supplies professionally.

B
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Old 15th Dec 2018, 11:22 pm   #19
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

Baz

I had a look at my 1 yr old Yaesu FP1030 linear PSU, and the circuit.
It's a 13.8V 25A fixed unit, without charge facility.

It has no EMC or transient protection, or soft start in the transformer primary, just a fuse, and thermostat in the mains wiring but physically attached to the DC regulator heatsink.

I loaded the PSU at 10A, and had a look at the DC output with a CRO.
I didn't see anything unusual, and no great spikes for mains on and off.

There may be just a little soft start circuitry in the DC regulator, but I couldnt see it at a glance, and the 12V turn on seems quick enough.

(Some DC PSUs have relay switched resistors in the primary for soft start, and others have relay or transistor switched controlled volts rise in the DC regulator).

And, ... just for everyone's interest, the DC bridge output capacitance is 10 x 4700 mfd!!

I couldn't measure the secondary winding wire exactly, caliper access being difficult, but it looked to me like 12 SWG or 2.5mm dia.
.
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Old 16th Dec 2018, 1:38 am   #20
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Default Re: Please ID: 250L9634, 250L9649. Varistors?

What's the mains on-off switch like? Mine has a very inexpensive looking rocker switch. Maybe that's involved. Also, I had no load on mine when I did my tests; I want to know what it does when my IC-718 is connected, but not switched on.

I've just wire in the suppressor C&R and the MOV, but not yet put in the scope.

B
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